1. Field of the Invention
The present invention relates to a signal processing apparatus and a signal processing method, a recording medium and a program. More particularly, the present invention relates to a signal processing apparatus, a signal processing method, a recording medium and a program which can use a narrow band filter and a wide band filter for accurately separating an input signal into a component of a sharp change in signal level with large edge and other components.
2. Description of the Related Art
Conventionally, in video cameras and the like, there is a method of improving contrast (a difference between brightness and darkness of image) of image data, sharpness (clearness of boundaries) and the like, emphasizing only components of the image data brightness signal without sharp change in signal level and large edge. Such method carries out a process for firstly separating the brightness signal into the component (edge component), in which the change in the signal level is sharp and the large edge is included, and the other component (nonedge component) and then emphasizing the nonedge component.
FIG. 1 is a view showing a configuration example of a conventional signal separator.
In FIG. 1, a signal separator 10 is provided with: a non-linear smoothing filter 11 for extracting the edge component of the input brightness signal; and an adder 12 for calculating a difference between the input brightness signal and the edge component in order to extract the nonedge component of the input brightness signal. It separates an input signal 21 into an edge component and a nonedge component, and outputs an output signal 31 composed of,the edge component and an output signal 32 composed of the nonedge component.
The non-linear smoothing filter 11 is provided with: a register group (not shown), which is composed of a plurality of registers each holding the brightness signal corresponding to one pixel, for holding the brightness signal corresponding to a pixel group in entirely continuous predetermined sections; and a selector group (not shown) for comparing the signal levels of the brightness signals outputted from the plurality of predetermined registers included in the register group and then judging whether or not a differentiated value between those signal levels is higher than a preset threshold.
Each of the selectors in the selector group built in the non-linear smoothing filter 11, if the differentiated value between the compared signal levels is higher than the preset threshold, outputs the signals of these pixels in their original states. If the differentiated value is less than the threshold, it smoothes the signals of these pixels to a predetermined level and outputs them. In other words, the non-linear smoothing filter 11 detects the change in the signal level higher than the preset threshold from the input signal 21, and judges that portion as an edge and outputs it in its original state, and smoothes and outputs the other portions as low amplitude components. Consequently, the non-linear smoothing filter 11 extracts the edge component from the input signal 21 and generates the output signal 31.
Also, the adder 12 subtracts from the output signal 31 extracted by the non-linear smoothing filter 11, from the input signal 21, and extracts the nonedge component, and then generates the output signal 32.
As mentioned above, the signal separator 10 separates the input brightness signal (input signal 21) into the edge component (output signal 31) and the nonedge component (output signal 32) and outputs them.